Up to now, as one of tire pressure detection systems (hereinafter referred to as TPMS: tire pressure monitoring system), there is a direct type tire pressure detection system. In the TPMS of that type, a transmitter equipped with a sensor such as a pressure sensor is attached directly to a wheel side to which a tire is attached. An antenna and a receiver are provided on a vehicle body side. When a detection signal from the sensor is transmitted from the transmitter, the detection signal is received by the receiver through an antenna to detect the tire pressure.
In such a direct type TPMS, there is a need to discriminate whether transmitted data belongs to a host vehicle, or not, and to which wheel the transmitter is attached. For that reason, ID information for discriminating whether the transmitted data belongs to the host vehicle or another vehicle and for discriminating to which wheel the transmitter is attached is allocated to data to be transmitted by the transmitter, individually.
In order to identify a position of the transmitter from the ID information included in the transmitted data, there is a need to previously register the ID information on each transmitter on the receiver side in association with the position of each wheel. For that reason, when rotating the tires or exchanging the tires for winter, there is a need to again register the ID information of the transmitter and a positional relationship of the wheels in the receiver, and a user cannot freely change the tires. Therefore, a system that can automatically register the ID information is required. Therefore, for example, Patent Literature 1 has proposed a technique for automatically registering the ID information.
More specifically, the device disclosed in Patent Literature 1 detects that the wheel reaches a predetermined rotational position (rotation angle) based on an acceleration detection signal of an acceleration sensor provided in the transmitter on the wheel side, and performs frame transmission from the wheel side. When the user performs a registration instruction operation, the passage of teeth of a gear rotated in conjunction with the wheel is detected by a wheel speed sensor, and the wheel position is identified based on a variation range of a tooth position at a reception timing of the frame.
In addition, there is another method to pay attention to respective reception frequencies of multiple pieces of received unknown ID information during a fixed period, and register ID information with a high frequency as ID information of the host vehicle. Also, there is a method to obtain a correlation of a travel pattern of the host vehicle with a temperature and a pressure in a tire based on temperature and pressure information in the tire included in a transmission frame including the multiple pieces of unknown ID information received, and register the ID information corresponding to the travel pattern of the host vehicle as the ID information on the host vehicle. Further, there is a method to place an antenna in the vicinity of each wheel, measure an intensity (RSSI) of a received radio wave when the antenna receives a frame, and register the intensity of a large value as the ID information of the wheel in the vicinity of the antenna.